Press roll for paper making machines and the method of making same



April 1938- R. E. CLEVELAND 2,114,072

PAPER MAKING MACHINES AND THE METHOD OF MAKING SAME Filed May 7, 1955 t9 2 SAND BLA TED ROLL- AV PA PER was CHEM/CAL L-Y ET'CHED ROLL uCHROMIUM PLATE.

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Patented Apr. 12, 1938 PATENT OFFICE PRESS ROLL FOR PAPER- MAKING MA-CHINES AND THE DIETHOD OF MAKING SAME Ralph E. Cleveland, Waterbury,Conn.

Application May 7, 1935, Serial No. 20,211

3 Claims.

The invention relates to certain improvements in press rolls for papermaking machines and in the method of making same, and has moreparticular reference to the upper rolls of multiple sets or pairs ofrolls employed for squeezing water from the wet pulp during themanufacture of the paper the object of the invention being the provisionof such a roll that will insure a better product, materially reducewastage or broke",

and that will outlast rolls heretofore employed for this purpose withoutmaterial impairment.

To these ends, the invention comprises the novel construction of pressroll and method of making same as hereinafter set forth in detail andmore particularly pointed out in the appended claims.

In a paper-making machine, after the paper is formed on the Fourdrinierpart, it is led through the press part, and then through the dryers. Thefunction of the Fourdrinier part of the machine is to form the web; therest of the machine removes the water from the wet paper. When a sheetof paper leaves the Fourdrinier part, it contains about 85% water; thepress part reduces the water content to about 65 or 70%, and the dryersreduce the water to about 7%.

In the press part of the machine, the sheet of wet paper is carried onfelts between the press rolls. These rolls are arranged in verticalpairs, and two, three or more pairs are used. The lower roll of eachpair is usually rubber-covered,

3 while the upper rolls have been made of maple,

cast iron, brass-jacketed cast iron, or granite.

Weights, operating through a system of levers,

pull the upper press roll down on the sheet of paper, in order tosqueeze out the water.

To obtain good paper, it is necessary that the upper press roll bestraight along its lower edge, that it be hard, that it be smooth, andthat it does not pick up paper. It must be straight in order to squeezethe water out evenly; it must be hard to reduce wear and keep itsoriginal contour; it must be smooth and free of scratches, to avoidmarking the paper, and it must pick up no paper fibres, in order toprevent spoiling the sheet these requirements perfectly. It has, n'found55 the porosity of the surface. This porosity, which running under it.No roll hitherto used fills all.

the greatest importance in the functioning of a traps air between theroll and the paper, prevents the latter from sticking, as it does to aperfectly smooth metal surface. The pores break up the capillary actionbetween the surfaces.

Although granite rolls thus have a better surface for functioning aspress rolls in paper making machines than any other material hithertoused, their use is not as trouble-free and inexpensive as could bedesired. For one thing, granite rolls are very expensive. Formed as theyare from a natural material, they tend to be nonuniform in texture.Often it occurs that a roll, when finished, develops or disclosescracks, which make it useless. Satisfactory granite rolls of course bearthe cost of the work performed on unsatisfactory ones. Moreover, theserolls are, compared to metal rolls, very fragile, and must be handledwith great care. When worn out they havepractically no scrap or salvagevalue. Due to the low compressive, tensile and bending strength ofgranite, and the non-uniformity due to its origin, rolls made of thismaterial must be made very massive, and hence heavy, in order to bestrong. The weight of the roll, therefore, is very great, and dependsupon its length, rather than upon consideration of the .operatingrequirements.

Metal rolls can be made hollow or solid, as required, in order to obtainthe desired weight, and this weight is independent of the dimensions ofthe roll. Such rolls'can be made to any desired size, and can easily bemade uniform. They have some scrap value, and originally cost less thanhalf as much as a granite roll of the same dimensions. In spitetherefore, of their surface short-comings, they have had some use.

I have now discovered that the mechanical advantages of a metal roll canbe combined with the surface advantages of a granite roll, by means of asimple and inexpensive process. I find that, if a metal roll is producedwith a roughened or indented surface, and thereafter is chromium plated,a porous permanent surface of the desired character is obtained. Such asurface may be obtained in a number of ways, for example, the surface ofthe roll may be sand blasted, or it may be etched by suitable chemicals.

These methods obviously produce a random distribution of the indentionsresulting therefrom.

Any desired degree of porosity may be obtained by variation in theetching or sand blasting process, or by the choice of basis metal, orboth. As a basis metal I may use cast iron, bronze, steel, or othermetal suitable from the point of view of strength, hardness, price, andso on. If chemical etching is the roughening process to be used, I cando this with any of the known etching materials, and, by the choice ofthe one most suitable to the basis metal and the result desired, byregulation of its concentration and of its temperature, and bypermitting the etching to proceed for a longer or shorter time, I cancontrol the type of pitting quite accurately. If sandblasting is theprocess to be employed, I can likewise regulate the type of pitting by asuitable choice of abrasive material, size of abrasive particle, airpressure, distance between gun nozzle and object, time of action, andother factors. I find it usually advisable to grind the roll after sandblasting or etching, in order to remove wire edges and loose particles.I then plate this surface with chromium to a thickness between .001 and.010, although thicker deposits are quite usable.

My invention can be explained more specifically by reference to theaccompanying drawing which shows, more or less diagrammatically, severalpress rolls having roughened surfaces (greatly exaggerated) with thepurview of the present invention. In this showing:

Fig. '1 is a vertical cross section through a pair of press rolls, theupper roll being provided with a porous surface which is chromiumplated;

Fig. 2 is an enlarged sectional view along the line 22 of Fig. 1,showing a roll which has been sand blasted prior to being chromiumplated, while Fig. 3 shows a modification wherein an upper press rollhas been chemically etched prior to being chromium plated.

In the several figures like parts are designated by like referencenumerals. The upper and lower press rolls are shown at I and 2,respectively. The paper web 3 is carried between the rolls by means ofthe felt 4. The pits produced by sand blasting are shown at 5 in Fig. 2,while 6 represents the layer of chromium plating. In Fig. 8 the pores orpits produced by chemical etching are shown at 1, these pores having ashape somewhat different from that of the pits 5 of Fig. 2. These poresor pits serve to trap air during the pressing operation, this airpreventing the wet paper from being pressed into the pits.

As a particular example of my invention, I shall describe the novelsteps in the manufacture of a press roll with the use of a sand blast.This roll was made of steel, and was ground to size. I sand blasted it,using as abrasive ground chilled iron, adjusting the conditions so as tocause the surface to be uniformly covered with pits or indentionsrunning from .005" to .040" in diameter, and of about half that depth. Ithen polished the roll enough to smooth the sharp edges raised by thesand blasting. The roll was then plated in the conventional chromic acidchromium plating bath, until a layer of chromium .005" thick wasdeposited. Thereafter, the roll was again polished to bring up itsluster.

It will be understood that the above description is merely illustrative,and that my invention is not to be limited to the specific materials,methods or dimensions therein given.

What I claim is:

1. A press roll for paper making machines, comprising a metal cylinderhaving a sandblasted, chromium-plated and polished surface containingindentions in random distribution therein, said indentions ranging indiameter from about 0.005 to 0.04 inch and in depth from about 0.002 to0.02 inch, the chromium plating having a thickness ranging from about0.001 to 0.01 inch.

2. In the manufacture of press rolls, the process which comprisesblasting the surface of a metal roll with projected abrasive particlesof sufficient size and velocity to produce indentions in said surfacehaving a depth ranging from about 0.002 to 0.02 inch and a diameterranging from about 0.005 to 0.04 inch, grinding the blasted surface toremove sharp edges, electroplating said surface with a layer of chromiumhaving a thickness ranging from about 0.001 to 0.01 inch and thenpolishing said surface, thereby producing a porous surface preventingthe picking up of paper fibres and having pores too small to leave animprint upon paper.

3. The process of claim 2 wherein the projected abrasive particles areof ground chilled iron.

RALPH E. CLEVELAND.

